1. Field of the Invention
This invention relates to a fuel additive composition. More particularly, this invention relates to a fuel additive composition containing a polyisobutenyl succinimide detergent additive and a carrier oil.
2. Description of the Relevant Art
It is well known in the art that liquid hydrocarbon combustion fuels, such as fuel oils and gasolines, tend to exhibit certain deleterious characteristics, either after long periods of storage or under actual operational conditions. Gasolines, for example, in operational use tend to deposit sludge and varnish at various points in the power system, including the carburetor or injectors and the intake valves. It is desirable, therefore, to find a means for improving liquid hydrocarbon fuels by lessening their tendency to leave such deposits.
U.S. Pat. No. 4,240,803 discloses a liquid hydrocarbon fuel composition comprising fuel and a detergent amount of an alkenyl succinimide prepared by reacting an alkenyl succinic acid or anhydride, wherein the alkenyl substituent is derived from a specific mixture of C.sub.16 -C.sub.28 a olefins, with a polyalkylene polyamine. This patent teaches that for unexpected effectiveness as a liquid hydrocarbon detergent, it is essential that the alkenyl group attached to the succinimide be derived from a mixture of C.sub.16 -C.sub.28 olefins obtained as the bottoms product from an olefin oligomerization.
European Patent Application No. 376,578 discloses a three-component additive composition for reducing carbon deposits in internal combustion engines comprising (a) a polyalkylene succinimide, (b) a polyalkylene, and (c) a mineral oil. Also disclosed is a liquid fuel composition containing such additive composition, as well as a method for cleaning a gasoline internal combustion engine utilizing this composition. The sole example disclosed in this European application shows the use of a polyisobutylene succinimide additive in intake valve and carburetor cleanliness tests. However, no mention is made in the example of the type of polyamine used to prepare the succinimide or the molecular weight of the polyisobutylene substituent.
British Patent No. 1,486,144 discloses a gasoline additive composition comprising (a) a hydrocarbyl-substituted succinimide, (b) a polymer of a C.sub.2 to C.sub.6 unsaturated hydrocarbon, and (c) a paraffinic or naphthenic oil. Example 1 of the British patent discloses a polyisobutylene succinimide, wherein the polyisobutylene group has a molecular weight of about 900 and the imide moiety is derived from diethylene triamine, in combination with a paraffinic oil and about 28 weight percent of polypropylene having a molecular weight of about 800. This British patent further teaches that all three components are essential to achieving a reduction in carbonaceous deposits. U.S. Pat. No. 4,039,300 discloses a composition for fueling an internal combustion engine equipped with at least one carburetor, which comprises a major amount of hydrocarbons boiling in the gasoline range, a minor amount of at least one detergent and a minor amount of mineral oil of lubricating viscosity comprising at least 50 percent by weight of aromatic hydrocarbons having an average molecular weight of 300 to 700, the detergent and oil being present in amounts sufficient to inhibit formation of deposits on the carburetor. Among the detergents disclosed are polyaminopolyalkylene alkenyl succinimides, preferably polyisobutenyl succinimides. Thus, the thrust of this patent is the use of an aromatic-rich mineral oil containing at least 50 percent aromatic hydrocarbons, in combination with known detergent additives.